Methods of making paper tissue, towel, and the like are well known, including various features such as Yankee drying, throughdrying, fabric creping, dry creping, wet creping and so forth. Conventional wet pressing/dry creping processes (CWP) have certain advantages over conventional through-air drying processes including: (1) lower energy costs associated with the mechanical removal of water rather than transpiration drying with hot air; and (2) higher production speeds which are more readily achieved with processes which utilize wet pressing to form a web. On the other hand, through-air drying processing has been widely adopted for new capital investment, particularly for the production of soft, bulky, premium quality tissue and towel products.
Throughdried, creped products and processes (TAD) are disclosed in the following patents: U.S. Pat. No. 3,994,771 to Morgan, Jr. et al.; U.S. Pat. No. 4,102,737 to Morton; and U.S. Pat. No. 4,529,480 to Trokhan. The processes described in these patents comprise, very generally, forming a web on a foraminous support, thermally pre-drying the web, applying the web to a Yankee dryer with a nip defined, in part, by an impression fabric, and creping the product from the Yankee dryer. A relatively permeable web is typically required, making it difficult to employ recycle furnish at levels which may be desired. Transfer to the Yankee typically takes place at web consistencies of from about 60% to about 70%. See also, U.S. Pat. No. 6,187,137 to Druecke et al. which includes disclosure of peeling a web from a Yankee dryer.
Some newer processes including fabric-creping and the use of creping adhesives are described in the following co-pending applications: U.S. application Ser. No. 10/679,862, entitled “Fabric Crepe Process for Making Absorbent Sheet” which application, incorporated herein by reference, discloses particular papermachine details as well as creping techniques, equipment and properties; U.S. application Ser. No. 11/108,375, entitled “Fabric Crepe/Draw Process for Producing Absorbent Sheet” also incorporated herein by reference, provides still further processing and composition information; U.S. application Ser. No. 11/108,458, entitled “Fabric Crepe and In Fabric Drying Process for Producing Absorbent Sheet” and U.S. application Ser. No. 11/104,014, entitled “Wet-Pressed Tissue and Towel Products With Elevated CD Stretch and Low Tensile Ratios Made With a High Solids Fabric Crepe Process” both of which are incorporated herein by reference, provide some further variation as to selection of components and processing techniques. Another co-pending application, U.S. Ser. No. 11/451,111, filed Jun. 12, 2006, entitled “Method of Making Fabric-Creped Sheet for Dispensers”, incorporated herein by reference, provides information on suitable drying and other manufacturing techniques.
It is well-known that a portion of the bulk of a paper web made by way of conventional wet pressing is usually imparted by creping wherein the creping adhesive coating plays an important role. Generally, the level of adhesion of the papermaking web to a dryer cylinder is also of importance as it relates to transfer of the web to a drying cylinder as well as control of the web in between the dryer and the reel upon which a roll of the paper is being formed. Webs which are insufficiently adhered may blister or, even worse, become disengaged from a drying cylinder and cause a hood fire. Moreover, insufficient wet-tack may lead to a transfer failure wherein the web fails to transfer to a drying cylinder and remains imbedded in a fabric causing shutdowns and waste of material and energy. Further, the level of adhesion of the papermaking web to the dryer is of importance as it relates to the drying of the web. Higher levels of adhesion reduce the impedance to heat transfer and cause the web to dry faster, enabling more energy efficient, higher speed operation; provided excessive build-up of adhesive is avoided. Note, however that some build-up is desirable inasmuch as adhesion of the sheet to the dryer occurs largely by means of creping adhesive coating deposited in previous passes.
It is important that the adhesive on the dryer remains wettable and excess deposits are avoided. Likewise, the tack properties must be sufficient, but not excessive, since the web needs to be removed from the drying cylinder.
Attempts to improve the performance of creping adhesives, including various approaches to the above-noted problems, have been described in the art. U.S. Pat. No. 7,048,826 to Archer et al., for example, describes a process of creping a fiber web wherein various creping adhesives and/or other performance additives are applied to certain zones on the surface of the creping cylinder. The zones are divided on the surface of the cylinder based on differences in the surface temperature under standard operating conditions, and the adhesives are selected to match the performance requirements in each zone. The process in Archer et al. reportedly improves inconsistencies in the adhesive coating, e.g., inconsistencies due to excessive adhesive build up or adhesive removal. A similar process is described in U.S. patent application Ser. No. 10/261,026 (Publication No. 2004/0060675) of Archer et al.
U.S. Pat. No. 6,991,707 to Hill, Jr. et al. relates to a method for manufacturing a creped fibrous web, where the creping adhesive on the drying cylinder comprises an ionene polymer. The ionene-containing adhesive is sprayed onto the creping cylinder in an aqueous medium. According to Hill, Jr. et al, the ionene adhesive improves runnability of the process because the ionene resins retain their adhesive properties over a wide range of moisture levels and temperatures.
Other references relevant to creping adhesives and creping processes include U.S. Pat. No. 6,911,114 to Lindsay et al., U.S. patent application Ser. No. 10/980,735 (Publication No. 2006/0090867) of Hermans et al See also, U.S. Pat. No. 5,187,219 to Furman, Jr.; U.S. patent application Ser. No. 10/806,205 (Publication No. 2004/0177940) of Archer et al., as well as U.S. patent application Ser. No. 10/833,473 (Publication No. 2005/0245669) of Clungeon et al.
Despite advances in the art, adhesive coatings on drying cylinders are exceedingly difficult to control in terms of build-up, re-wettability and tackiness because the coatings are largely water and dry concurrently with the wet paper.